fix: migrate old null org_names

internal/store/postgres/migrations/20251030120000_convert_null_org_name_to_empty_string.down.sql

@@ -0,0 +1,18 @@
+-- Temporarily drop immutability trigger to allow update
+DROP TRIGGER IF EXISTS trg_audit_records_enforce_immutability ON audit_records;
+
+-- Convert empty string org_name values back to NULL
+UPDATE audit_records
+SET org_name = NULL
+WHERE org_name = '';
+
+-- Recreate immutability trigger
+CREATE TRIGGER trg_audit_records_enforce_immutability
+    BEFORE UPDATE ON audit_records
+    FOR EACH ROW EXECUTE FUNCTION prevent_audit_record_updates();
+
+-- Restore partial index condition to original
+DROP INDEX IF EXISTS idx_audit_records_org_name;
+CREATE INDEX idx_audit_records_org_name
+    ON audit_records(org_name, occurred_at DESC)
+    WHERE org_name IS NOT NULL;

internal/store/postgres/migrations/20251030120000_convert_null_org_name_to_empty_string.up.sql

@@ -0,0 +1,18 @@
+-- Temporarily drop immutability trigger to allow update
+DROP TRIGGER IF EXISTS trg_audit_records_enforce_immutability ON audit_records;
+
+-- Convert all NULL org_name values to empty strings
+UPDATE audit_records
+SET org_name = ''
+WHERE org_name IS NULL;
+
+-- Recreate immutability trigger
+CREATE TRIGGER trg_audit_records_enforce_immutability
+    BEFORE UPDATE ON audit_records
+    FOR EACH ROW EXECUTE FUNCTION prevent_audit_record_updates();
+
+-- Update partial index condition to exclude both NULL and empty strings
+DROP INDEX IF EXISTS idx_audit_records_org_name;
+CREATE INDEX idx_audit_records_org_name
+    ON audit_records(org_name, occurred_at DESC)
+    WHERE org_name IS NOT NULL AND org_name != '';